Hypothermia protects neurons against damage induced by nitric oxide in the retina of rats subjected to perinatal asphyxia

CAPANI, F.; REY FUNES M.; AON L.; SARACENO, E.; BOTI, V.; LOIDL C.F.; RODIRGO J; GIRALDEZ, L.; COIRINI, H.

Hilton Buenos Aires, Puerto Madero, Ciudad Autónoma de Buenos Aires, Argentina

Congreso; XVII International Congress of Eye Research; 2006

International Society for Eye Research

Brain hypothermia is at the present one of the most effective treatment against brain global hypoxic-ischemia. Perinatal asphyxia (PA) induces retinal alterations that we have shown previously are compatible with the pathological changes observed in the phase II of the Retinopathy of the Prematuriy (ROP). Since the insufficient vascularization is on of the factor involved in retinopathy ischemic abnormalities, we studied short and long term nitric oxide (NO) modifications in the retina after severe PA. We also investigated the effect of hypothermic treatment on these changes by combining immunohistochemistry, western blot, enzymatic activity and electron microscopy analysis. Retinal sections from 21 days, 30 days and 60 days old animals subjected to PA for 20 min. at 37°C and 20 min. of PA at 15°C (hypothermia) were stained using antibody against nitric oxide synthase isoform (nNOS), inducible nitric oxide isoform (iNOS) and nitrotyrosin (ntr). Further analysis of the data was conducted using a Scion Image Beta. After PA we observed in the sections stained for nNOS a significant increment (30%; p< 0.01) of the relative optic density (ROD) starting at 21 days. At 30 and 60 days NOS immunoreactivity was increased within the same values than we have detected at 21 days. We have found the same changes after PA when we stained the tissue for iNOS. Electron microscopic studies of control and PA showed a ganglionar cell death a strongly related with we observed at light microscopic level in Nissl stainedmaterial. We also observed a significant increment in the ROD for nitrotyrosin immunoreactivity after PA in ganglion neurons in the 3 time points studied (25 % more than in control p< 0.01). Since nitrosylation is an indicator of peroxinitrite production this data is consistent with the ganglion cells death observed at long term PA. Furthermore western blot and enzymatic activity for NO analysis confirmed these observations. Decreasing the temperature from 37 °C to 15 °C dramatically prevented the alterations during the hypoxic insult since the analysis of the data showed the same results that we observed in control conditions. Taken together these results suggest that NO could be involved in the hypoxic pathological changes on the rat retinas. Furthermore we propose that deep hypothermia treatment reduces the NO changes and cell death thus showing an excellent efficiency as possible therapeutic agent for retinal alterations induced by hypoxia during PA. Supported by UBACYT M020, CONICET 5784, ANPCyT 15001 and Karolinska Foundation.